With people's increasing demand for life quality, hygiene also becomes an important issue in their daily living, this is especially obvious to public sanitary facilities. In the past, many public sanitary facilities must be operated manually by users. Continuous progress has been developed these years that sensors have been deployed to automatically detect user's using conditions. Formerly after the user has finished hand washing, water remained on the hands could drop around, thus paper towel has been produced to dry hands after washing. However, with increasing awareness of environmental protection and preservation, trees become precious resource. As a result, using hand dryers to replace paper towel gradually becomes a trend.
At present, there are myriad types of hand dryers on the market. The hand drying principle is mainly to use a motor which rotates the blades to suck the air in, heat the air and then exhaust the heated air to dry user's hands. For instance, R.O.C. patent Nos. M357271 and 579813 respectively disclose a hand dryer that has an air outlet on the exterior to exhaust air to dry user's hands. The hand dryer has only one air outlet to exhaust the air in one direction, and hence it cannot dry user's hands quickly. Moreover, the air exhaust range of the air outlet is too small and air exhaust volume is limited, and hence a greater amount of electric power has to be consumed to fully dry the hands.
U.S. Pat. No. 7,555,209 and WO 2007/020699 respectively disclose a hand dryer that has multiple air outlets at two corresponding sides of the hand drying area to form a bidirectional air exhaust structure to increase the hand drying area. The bidirectional air exhaust structure exhausts the air to dry user's palms and backs of hands at the same time. While such a design increases the number of the air outlets and exhausts the air bidirectionally to increase the hand drying area and save hand drying time to overcome the problems in the conventional hand dryer with single air outlet and unidirectional air exhaust, it still has drawbacks in use. The airflow generated by the bidirectional air exhaust hand dryer can blow merely two opposite sides of user's hands but not all-round airflow. User's hands have to be moved slowly up and down during drying; however, even if the palms and backs of the hands have been dried, hand crevices, such as finger gaps and finger nails could still be wet. To fully dry the hands is desired, user has to constantly and slowly move the hands up and down.